1. Field of the Invention
The invention relates to a technical field for a crystal oscillator for surface mounting (hereinafter called a surface-mounted oscillator), and in particular, to a surface-mounted oscillator whose mounting terminals onto the set substrate are also used as crystal testing terminals.
2. Description of the Related Art
Surface-mounted oscillators are compact and lightweight. Therefore, the surface-mounted oscillators are particularly adopted as reference sources for frequency and time in portable electronic devices. As one of these, there is a surface-mounted oscillator configured such that an IC chip and a crystal element are housed in a case main body, and a crystal testing terminal to measure the vibration characteristics of a crystal unit is provided on the outer surface thereof (for example, refer to JP-A-2007-142869).
FIGS. 6A to 6C and 7 are diagrams for explanation of one related example. FIG. 6A is a front view of a surface-mounted oscillator, which is partially fractured cross-sectionally, FIG. 6B is a schematic bottom view of the same, and FIG. 6C is a plan view of a crystal element. FIG. 7 is a diagram of an oscillator circuit for clock.
The surface-mounted oscillator 200 is configured such that an IC chip 2 and a crystal element 3 are housed in a case main body 1 which is formed to be concave, and a cover 4 is jointed thereto so as to hermetically encapsulate those. The case main body 1 is formed of a laminar ceramic, and for example, has an inner wall shoulder portion on one end side. The four corners of the outer bottom face of the case main body 1 has mounting terminals 5 composed of a power supply terminal 5(Vdd), an output terminal 5(OUT), a ground terminal 5(GND) and a function terminal. Here the function terminal is set as a standby terminal 5(ST).
The IC chip 2 is configured such that an oscillator circuit 6 shown by the dotted frame in FIG. 7 (except for the crystal unit 3A) is integrated, and is composed of an oscillator stage 6a, an output circuit 6b, and a standby circuit 6c serving as a function circuit. The oscillator stage 6a has an oscillating amplifier 7 composed of an inverter element made to be a CMOS, for example, and capacitors C (Ca and Cb) forming a resonant circuit with a crystal unit 3A. Reference code Rf in the drawing is a feedback resistor, and a plurality of reference codes 21 indicated by mark “□” provided on the line of the dotted frame are IC terminals.
The output circuit 6b is configured such that a plurality of buffer amplifiers 8 composed of inverter elements (CMOS or the like) are series-connected to the oscillating amplifier 7, to amplify an oscillating output so as to shape a waveform into a rectangular form, for example. The standby circuit 6c is used in a case in which the surface-mounted oscillator 200 is particularly used for clock, and operates or stops the oscillating amplifier 7 and the buffer amplifiers 8 as needed. Thereby, power consumption is reduced.
In this case, the standby circuit 6c operates on the basis of a control signal (LOW or HIGH) from the standby terminal 5(ST). Then, based on the standby circuit 6c when a control signal from the standby terminal 5(ST) is LOW or HIGH, the oscillating and buffer amplifiers 7 and 8 are operated or stopped.
The circuit functional surface having the IC terminals 21 of the IC chip 2 is fixed to the inner bottom face of the case main body 1 (so-called flip-chip bonding). For example, a metal bump 9 provided to the IC terminals 21 is electrically and mechanically connected to the circuit terminals provided to the inner bottom face of the case main body 1 by ultrasonic thermo-compression bonding or the like. The power source, output, ground, and standby terminals of the IC terminals 21 are electrically connected to respective mounting terminals 5 {5(Vdd), 5(OUT), 5(GND) and 5(ST)} on the outer bottom face of the case main body 1 through wiring routes.
The crystal element 3 has excitation electrodes 10 (10a and 10b) on its both principal surfaces, and for example, extraction electrodes 11 (11a and 11b) are extended on the both sides of one end of the crystal element. Then, the both sides of the one end of the crystal element 3 on which the extraction electrodes 11 (11a and 11b) extend are firmly fixed to a pair of crystal holding terminals (not shown) provided to the inner wall shoulder portion of the case main body 1, with a conductive adhesive 12.
The pair of crystal holding terminals is electrically connected to the crystal terminals of the IC terminals 21 through wiring routes. Then, the pair of crystal holding terminals is electrically connected through the lamination plane to crystal testing terminals 13 provided to the lateral surfaces of the case main body 1 facing each other. Thereby, the excitation electrodes 10 of the crystal element 3 are connected in parallel to, not only the crystal terminals of the IC terminals 21, but also the crystal testing terminals 13.
The cover 4 is jointed to the end face of the opening of the case main body 1 by seam welding or the like, to hermetically encapsulate the IC chip 2 and the crystal element 3. Then, a probe out of a measuring apparatus (not shown) is made to contact the crystal testing terminals 13 of the case main body 1, to test the vibration characteristics including a crystal impedance (CI) and the like of the crystal unit. Note that, because the vibration characteristics vary due to stress and the like at the time of joining the cover 4, the vibration characteristics after encapsulating with the cover are to be tested.
However, in the related surface-mounted oscillator 200 having the above-described configuration, in particular, the more the downsizing thereof is advanced, for example, as the planar outline thereof comes to be 2.0×1.6 mm or less, the areas of the crystal testing terminals 13 become smaller. Thus, it makes more difficult to contact the probe of the measuring apparatus to the crystal testing terminals 13. Further, because the crystal testing terminals 13 have essentially no need for an operation of the surface-mounted oscillator 200, and the case main body 1 has the crystal testing terminals 13 on its lateral surfaces, they may be a cause for generating floating capacitance, which may produce a problem exerting an effect on an oscillating frequency.